Here we go again.
17 years, that's how long we have known on line within the web community that PO4 (elevated levels) do not induce BBA or any number of algae.
This is not a question, this is a fact.
If you use basic logic, I'm talking the exact same type used in Science, we should be able to add PO4 and get BBA(or any algae that many claim).
You made the hypothesis, now try and test this.
There are many potential causes.
But.......all it takes are few cases where we KNOW we add plenty of PO4 and do not get BBA, that this hypothesis is falsified.
I really wish history would not repeat itself and that each new cohort of planted hobbyists seems to have to go through this all over again and again ad aduseum
If the hypothesis is true, then where is my BBA?
I dose 10 ppm a week and feed fish.
I sell gobs of Starougyne, Red pantanal, mini butterfly, Rare Cryptds, a mix of both slow and fast growers. Check out the feedback if you have even a little doubt. So that's one aspect totally falsified multiple times for going on 2 decades.
So what is going on then?
Same deal as way back then when Kevin and Paul suggested it.
The hobby is about growing plants, not limiting algae.
Never was about limiting algae, it's still not.
Liebig's law applies:
What you have done however is limit the plant growth itself.
Instead of CO2 being the MOST limiting factor, now you have switched to PO4 being the MOST limiting factor.
A decent image of the concept:
Now if you could/can manage CO2 correctly, and have enough control with CO2, then BBA is not an issue. I've never once seen otherwise. Not in some 20 years.
So when you limit PO4, now your CO2 issue went away(and thus the BBA goes away, as if by magic? I think not, I have always linked BBA to the poorly managed CO2 levels(bobbing between say 5-15 ppm etc for some/all of the lighting period).
This also confirms that CO2 is likely the inducer of BBA. There may be other factors involved with BBA, but I;'ve not seen any that are testable other than CO2.
You never limited BBA with PO4 remover, that much is clear. You reduced the demand for CO2 by the plants. Plants can tolerate PO4 limitation much better than they can CO2 limitation.
So it goes back to plant growth and Liebig.
You will not escape that.
To have a good understanding and horticultural ability, good usage of CO2 is key. Now if you cannot use CO2 well, too impatient, not enough/too much current, have poor equipment, assume test kits are correct and do not pay more attention to the plants, algae and fish properly, well..........then you might need a crutch like PO4 limitation.
It works but fails to grow plants really well and fails to teach the hobbyists how to manage CO2 correctly.
Now if you also add a lot of light, then you'd expect you'd also require more CO2, and many folks seem to have that vs low light, good CO2 and ferts.
This article discusses light and CO2 demand independent of nutrients:
1 st thing they discuss: Liebig, go figure.
There are thousands of aquariums with non limiting PO4 out there that are free of BBA, a number of folks going "me too" does not suggest much other than poor CO2 management frankly. Sounds harsh? It should. It was clearly shown to be FALSE decades ago. We can never know with absolution what causes something(say BBA), but we can say what something is not.
Explain why my tanks do not have BBA.
You cannot with that hypothesis.